When you are troubleshooting a network, you can easily see the MAC addresses entering each interfaces on a switch. The command to do so on Cisco is:
#show mac address-table interface g1/1
But if you want to know more about the device associated with this MAC address, you are going to have to use one simple tricks.
You can always google the first six characters of this MAC address to find out the vendor associated with it. But to find its IP address, here’s what you need to do:
Ping the broadcast address of the vlan this device is probably in. When you ping the broadcast address, all layer 3 devices in that subnet will respond. Make sure you are pinging the broadcast address from a switch that has a IP address in that specific vlan.
That is because if it is in the same subnet, it will use the ARP protocol to link each MAC address with its corresponding IP address. You can see the ARP table on Cisco with this command:
To show only the IP address associated with a specific MAC address, use the include keyword:
#show arp | include aaaa.bbbb.cccc